1. Field of the Invention
The present invention relates to IC memory cards that comply with PC card standards and are used for external storage media for information processing equipment such as notebook personal computers, portable terminal units, and the like.
2. Description of the Related Art
FIG. 10 is a block diagram illustrating an example of prior IC memory cards. In FIG. 10, an IC memory card 100 comprises a memory section 103 that stores data from a host system apparatus 101 and an interface section 102 that complies with PC card standards and interfaces with host system apparatus 101. Host system apparatus 101 consists in an information processing apparatus. Interface section 102 comprises an address bus buffer 104, an address decoder 105, a card mode controller 106, and a data bus buffer 107. Address bus buffer 104 and address decoder 105 are connected to host system apparatus 101 through an address bus 108. Card mode controller 106 is connected to host system apparatus 101 through a control bus 109. Data bus buffer 107 is connected to host system apparatus 101 through a data bus 110.
Further, address bus buffer 104 is connected to memory section 103 through an internal address bus 111. Card mode controller 106 is connected to memory section 103 through a plurality of signal lines 112. Data bus buffer 107 is connected to memory section 103 through an internal data bus 113. Address decoder 105 is connected to card mode controller 106, which is connected to data bus buffer 107.
In this construction, address bus buffer 104 receives address data from host system apparatus 101 through address bus 108 and outputs the input address data into memory section 103 through internal address bus 111. Further, address decoder 105 also receives the address data from host system apparatus 101 through address bus 108 and decodes the address data to output the decoded address data into card mode controller 106.
In addition to the decoded address data from address decoder 105, card mode controller 106 is also provided with a card-mode control signal comprising an output-enable signal, a write-enable signal, and a card-enable signal by host system apparatus 101 through control bus 109. Card mode controller 106 then generates from these signals a memory control signal, which consists of an output-enable signal, a write-enable signal, a chip select signal, and the like, for controlling memory section 103, and also generates an I/O control signal. Card mode controller 106 then outputs the memory control signal into memory section 103 through signal lines 112 and outputs the I/O control signal into data bus buffer 107.
Data bus buffer 107 performs I/O control, in data bus 110 and internal data bus 113, of data between host system apparatus 101 and memory section 103 based on the I/O control signal input from card mode controller 106. Further, memory section 103 performs the writing and reading of data through internal data bus 113 based on the address data input through internal address bus 111 and the memory control signal input through signal lines 112.
In a system having IC memory cards as its external storage media, data stored in an IC memory card is usually enciphered for security protection. In this case, for the above IC memory card 100, host system apparatus 101 has to encipher and decipher the data, so that the load of host system apparatus 101 becomes great. Further, host system apparatus 101 requires a large-scale system construction to use up great amounts of cost, labor, and time.